JPS6266132A - Discoloration time managing layer - Google Patents

Abstract

PURPOSE:To control freely a discoloration start time by interposing a polymer containing >=30mol% methyl methacrylate, between a layer containing a microcapsule of an oily substance, and a layer containing a substance which is discolored by contacting to said layer. CONSTITUTION:A discoloration start time which occurs after breaking down a microcapsule is controlled freely by providing a discoloration time managing layer consisting of a high polymer film in which an indispensable monimer component is methyl methacrylate, between a layer A containing the microcapsule of an oily substance, and a layer B containing a substance which causes a discoloration by contacting to a component in the microcapsule, on a supporting body. In such a way, even if the layer is exposed at a set temperature or above, a due guidance time can be provided until the discoloration is started, and a discoloration time managing layer which is suitable especially for an indicator whose coloring time is 2-8hr is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a color change time management layer.

More specifically, it is located between the layer [A] comprising microcapsules of a liquid substance and the layer CB) comprising a substance that causes discoloration upon contact with the components in the microcapsules, and destroys the microcapsules. The liquid substance that flows out is
B] Concerning the discoloration time control layer that controls the time required to reach the layer and cause discoloration, it is used as a temperature control indicator label for items that require strict temperature control such as refrigerated or frozen foods. Useful for color change time management.

[Conventional technology]

For articles requiring temperature control, it has been desired to develop storage temperature control labels that irreversibly change color when temperatures exceed a predetermined temperature. Examples of items that require temperature control include frozen foods, refrigerated foods, fresh flowers, and pharmaceuticals. No means have been found at this stage. In addition, even though it is necessary to strictly control the temperature of products such as frozen and refrigerated foods, it is important to know whether the product is stored under the necessary temperature control and delivered to the user after being manufactured. This is difficult, and related industries are in need of a specific temperature management system.

The applicant has previously conducted extensive research to solve these problems, and has applied an irreversible coloring system that uses a methine dye precursor and oxidizing material to a temperature display unit, and has developed a highly distinctive and effective color system. proposed a new unit (Japanese Patent Laid-Open No. 30-53984).

In other words, the unit uses (1) a hydrophobic organic substance of any melting point, (2) a methine dye precursor, and (6) an oxidizing material typified by a benzoquinone derivative as essential constituent materials. A temperature control label using a temperature control unit supports the above-mentioned microcapsules (1), (2) and (3), or microcapsules obtained by dissolving (2) in (1), and (5) as essential components. It is something that is held on the body.

Although such units are extremely effective in performing strict temperature control, they still have the following problems in actual distribution processes. In other words, if the target item is stored at a specified temperature, it will rot or deteriorate due to the proliferation of bacteria, etc., and it can be used to easily detect such temperature history. For example, in the case of refrigerated foods, indicators (labels or tags) are generally attached to the surface of the package where the target food, such as meat or fish, is packaged with a polymeric material or the like. 1
Indicators are immediately exposed to the storage environment temperature, but meat, fish, etc. that are originally subject to management do not immediately follow the environmental temperature due to their own specific heat or the heat shielding effect of the packaging container, and the temperature changes over time. causing delays. −
! fc, even if the target product follows the environmental temperature, it does not immediately rot or change in quality and become inedible, and depending on the target product, there is a permissible storage time during which the product can remain edible. Generally, refrigerated foods (10
Even if food is exposed to an environmental temperature of 10°C or higher for a short period of time, such as 5 or 30 minutes, it does not render it inedible. Therefore, units that develop color even when exposed to temperatures above the control temperature for a short period of time cannot be used as indicators as described above, and should be used as indicators of the time it takes to change color depending on the purpose, such as the decomposition behavior of the target item. It is desired to develop a system that can control the

The inventor of the present invention discovered that the above-mentioned problems could be solved by a color change time management layer made of a polymer film containing a specific amount of acrylonide IJ, and filed a patent application (Japanese Patent Application No. 110297/1983). issue).

[Problem that the invention seeks to solve]

The above-mentioned allowable heat retention time varies considerably depending on the target product.For example, the allowable heat retention time for certain types of pharmaceuticals and catalysts is extremely short, 15 to 30 minutes, but for other products, such as tofu and natto. For some foods, the A'c' period is 4 to 6 hours, and for others it is even longer, 20 to 50 hours. An indicator with a color change time is required.

The present invention was made from such a viewpoint, and an object of the present invention is to provide a color change time management layer suitable for an indicator having a color development time of 2 to 8 hours, particularly 4 to 6 hours.

[Means for solving problems]

Based on the knowledge of the previous temperature control unit, etc., the present inventors
As a result of intensive research into simple indicator labels that can control product temperature, we found that the A3 layer, which contains microcapsules of an oily substance on a support, causes discoloration when it comes into contact with the components present in the microcapsules. By providing a discoloration time management layer made of a polymer film containing methyl methacrylate as an essential monomer component between the [39 layer] and the layer [39], the discoloration start time that occurs after the microcapsules are destroyed can be freely controlled. We have discovered that scales can be controlled, and have arrived at the present invention.

As mentioned above, the color change time management layer of the present invention is a polymer film using methyl methacrylate as an essential monomer. A general term for products obtained by copolymerizing methyl methacrylate as an essential monomer component and, if necessary, copolymerizing other ethylenic monomers by methods such as radical polymerization. Among various polymerization methods,
Radical polymerization is preferably used, and it is most commonly produced in the form of a water-dispersible polymer emulsion (hereinafter referred to as "acrylic emulsion") obtained by emulsion polymerization using a redox catalyst in an aqueous medium. . The specific composition of such acrylic emulsion is:
A homopolymer or copolymer containing 30 moles or more of methyl methacrylate, the components to be subjected to copolymerization are (a) acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Ethylenically unsaturated carboxylic acids such as (b) Aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, divinylbenzene (C) Methyl acrylate, ethyl acrylate, methyl acrylate, 2-ethylhexyl acrylate, methacryl alkyl esters of acrylic acid or methacrylic acid, such as ethyl acrylate, butyl methacrylate, 2-ethylhexyl methacrylate; (d) hydroxyethyl acrylate;
(e) Derivatives of acrylamide or methacrylamide such as acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diacetone acrylamide, vinylpyrrolidone,
Examples include various monomer components such as glycidyl acrylate, glycidyl methacrylate, vinyl acetate, vinyl chloride, vinylitine chloride, acrylonitrile, and methacrylonitrile. Further, in addition to the above-mentioned nonionic or anionic monomers, cationic vinyl monomers such as trimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and triethylaminoethyl methacrylate may be mentioned. Of course, the components used are not limited to these exemplified compounds. Of course, various multicomponent copolymers of three or more monomers are also preferably used in the color change time management layer of the present invention. Of course, the use of a mixture of two or more copolymers also falls within the scope of the present invention.

These components used together with methyl methacrylate may be polymerized in a mixed state in advance, monomers may be added stepwise to perform block copolymerization, or graft copolymerization may be performed, and the monomers used may be water-soluble. In the case of a functional component, it may be added in advance to an emulsion of a homopolymer or copolymer of methyl methacrylate and then further polymerized.

A polymer containing methyl methacrylate as an essential component of 30 or more moles, preferably 50 or more moles is used as the color change time management layer of the present invention.

The acrylic emulsion essentially containing methyl methacrylate obtained by the emulsion polymerization method used as a preferred embodiment of the present invention has an average particle diameter of OD1 to 10.
It is obtained as a white water suspension of fine particles of μ, preferably 0.05 to 05 μ, and has the property of causing polymer particles to fuse together to form a uniform film when the water evaporates during drying. It is.

The polymer used in the present invention is applied to a support by coating or the like, and then dried to form a film to become a color change time control layer. In order to effectively form a continuous film by forming a film, it is preferable to use a polymer having a glass transition point of 30° C. or lower, preferably 30° C. or lower.

Specifically, the color development time management layer of the present invention is used by contacting the [A] layer comprising microcapsules of an oily substance provided on a support with the components in the microcapsules to cause discoloration. CB) layer containing a substance.
Ru. The support is generally a flexible film-like material such as paper or polymer, and the [A] layer or CB) layer is generally applied as an upper layer using various coating methods, such as air knife coach ink, bar coating, etc. It is provided by methods such as coating, grade coating, gravure coach ink, roll coat ink, or various printing methods such as gravure printing, flexo printing, offset printing, screen printing, etc. A color development time management layer made of a polymer containing methyl methacrylate of the present invention as an essential component is provided on top of the layer, and a coating method is generally used. In a preferred embodiment, when an acrylic emulsion is used, it is obtained as a low viscosity aqueous suspension;
Coating methods suitable for applying low viscosity coating liquids, such as air knife coaters and bar coaters, are generally preferred. The color development time management layer of the present invention has a dry thickness of 0.01
It is in the form of an extremely thin continuous film of ~20μ, preferably about 0Jll15~10μ, and is provided by applying the coating method described above and then drying at a temperature raised to a temperature at which a continuous film can be sufficiently formed. Furthermore, a layer CB) or a layer [A] is provided above it. These layers are also provided by coating or printing.

In the label-like product provided with the color development time management layer of the present invention, the time-controlled discoloration area is required to be in the form of letters or pictures, so when printing, especially when printing microcapsules, Printing methods that can cause microcapsules to break due to pressure are disadvantageous, and clean printing methods are most preferably used.

The acrylic emulsion is a composition that is the main component of the color change time management layer provided between the microcapsule layer of the oily substance and the color developer layer, and has properties that play a role in controlling swelling, diffusion, penetration, etc. of the oily substance. It must have the following characteristics. Incidentally, a resin film with a large barrier effect itself does not allow oily substances to pass through, so it is not suitable as the discoloration time control layer of the present invention, and a resin film with a too small barrier effect allows oily substances to pass through. , which is still unsuitable as the color change time management layer of the present invention. In other words, in order to be able to serve as the color change time control layer required in the present invention, it must have both appropriate barrier properties and appropriate carrier properties. In other words, the purpose is achieved by using the acrylic emulsion.

Here, methyl methacrylate is an essential component, that is, methyl methacrylate is contained at least 30 mole, preferably at least 50 mole.
If it is less than 100%, the function as the color change time management layer of the present invention is insufficient, that is, the oily substance penetrates quickly, and the conditions for the time management layer targeted by the present invention are not yet met.

For this reason, a layer containing methyl methacrylate of 30 mole or more is effective as the color change time management layer of the present invention, and is an effective means for achieving the object of the present invention.

In the present invention, as means for causing discoloration, for example, color development using a methine dye precursor and a benzoquinone derivative as proposed in JP-A No. 30-53984, or color development using a phthalide derivative and an organic or inorganic solid acid is used. be able to. For example, one of these color-forming components is dissolved in a hydrophobic organic compound having a melting point near the temperature that requires control to form an oily substance, microencapsulated by a known method, and incorporated into the [A] layer, CB the other
'It may be contained in one layer. Alternatively, the hydrophobic organic compound may be microencapsulated and contained in the [A] layer, and both coloring components may be contained in the CB) layer. Variations of these may also be used. Various hydrophobic organic compounds are used depending on the purpose, but for example, n-butyl caprate is a nonvolatile hydrophobic organic compound that has a sharp melting point in the range of -30°C to +50°C. , n-ethyl caprate, n-dodecyl acetate, ethyl n-undecanoate, n-decylbenzene, undecyl caproate, heptyl caprylate, n-butyl laurate, myristic acid.
Examples include 0-butyl, n-dodecylbenzene, methyl laurate, ethyl myristate, isobutyl palmitate, n-butyl valmitate, and methyl myristate.

In addition to the microcapsules and substances that cause discoloration, the [A] and [39] layers contain natural or synthetic polymeric binders, solvents, and inorganic or organic fillers for the purpose of improving coating and printability. It is common to include

When the temperature indication label provided with the color development time control layer of the present invention is used (activation of the temperature control function), the microcapsules are destroyed by roll pressure, impact pressure, etc. When the temperature exceeds the control temperature, the substance within the microcapsules melts and begins to change color after passing through the color development time control layer of the present invention by dissolution, osmosis, and diffusion. The time required for the start of discoloration varies depending on the viscosity, polarity, molecular weight, etc. of the oily substance within the microcapsules, so the monomer composition, particle size, molecular weight, and coating thickness of the time management layer to be used should be adjusted depending on the time required for the start of discoloration. Change and respond.

〔Example〕

This will be explained below using synthesis examples and examples. Note that parts are % by weight and parts by weight unless otherwise specified.

Synthesis example 1 [v] was prepared from sample (1) by the method described below.

Attach a stirrer to a round-bottomed flask with a heating device attached.Water 491.27 and sodium dodecylbenzenesulfonate 1.
2DfI was added, and 1 potassium persulfate was added as a polymerization catalyst.
．． 2y, add 0.62% of sodium bisulfite and raise the temperature to 70°C with slow stirring, then add 25% of methyl methacrylate.
9.0y, butyl acrylate monomer 136. OS+
, 2-ethylhexyl acrylate monomer 95.91
A mixture of 31 parts of acrylic acid and 6.0 parts of acrylamide was added at a rate of 42 parts per minute using a charge pump, and 5 hours after monomer charging, a white cloudy acrylic emulsion 10002 (average particle size 035 μm) was obtained.

This had a concentration of 495 moles and 61 moles of methyl methacrylate in the dietary supplement. This is sample CI
].

Synthesis Example 2 Using the same apparatus as Synthesis Example 1, 526.5y of water and 10.5y of dodecylbenzenesulfonic acid sorter were added. Of woka, t, and 1/1 potassium persulfate and 0.5 sodium hydrogen sulfite as polymerization catalysts? After adding and raising the temperature to 65°C, 203.2y of methyl methacrylate and 147.2y of butyl acrylate monomer were added.
4y,2-ethylhexyl acrylate monomer 105
．． 9y, a mixture of acrylic acid 5.52% was added at a rate of 5t/min using a charge pump, and 7 hours after monomer charging, an acrylic emulsion 10 became cloudy white.
001 (average particle size 0.30μ) was obtained. This one is 4
With a concentration of 6.2%, ethyl methacrylate was 53 moles of total monomer. This is designated as a sample (It).

Synthesis Example 3 547.5 y of water and 82 y of sodium dodecylbenzenesulfonate were processed using the same equipment as in Synthesis Example 1, and 1.0 y of potassium persulfate and 0.52 y of sodium bisulfite were added as polymerization catalysts, and the temperature was raised to 75°C. , methyl methacrylate 1
39.4y, butyl acrylate monomer 188.11
．． 2-ethylhexyl acrylate monomer 9461,
A mixture of 3.62% of acrylamide and 2.22% of acrylic acid was added at a rate of 62% per minute using a charge pump, and 1000 y of a white cloudy acrylic emulsion (average particle size of 025μ) was obtained 4 hours after monomer charging. Ta. This also had a concentration of 0.14443%, with methyl methacrylate being 38 moles of total monomer. This is referred to as sample (l[).

Synthesis Example 4 In a 200-piece stainless steel beaker, add 10% polyvinyl alcohol 1 aoylr FLζ and r-2,s-di-n-phthoxycarbonyl-6,6-cyphenylsulfonyl 1
, 4-benzoquinone 1f was added and stirred at high speed (1100
0RP) for 3 hours to obtain a developer dispersion.

50 yen of water in another container? , 207.10% calcium carbonate, 20y of starch and 10y of a color developer dispersion were added thereto, and after stirring and mixing, a coating liquid having a solid content of 23% and a viscosity of 150 centipoise was obtained. This is designated as sample [■].

Synthesis Example-5 4,4'-bis-dimethylamino-? -Methyl-4#-
Myristic acid ethyl ester in which 2% ethoxytriphenylmethane was dissolved was coated with a melamine resin film by a known polymerization method to obtain a microcapsule slurry (average particle size: 4.0 μm, solid content: 50 μm). %). 17-10 parts of the microcapsule slurry, 20 parts of styrene-butadiene latex, and 100 parts of water were mixed to obtain a capsule-containing coating liquid. This is designated as sample [v].

Acrylic emulsions obtained in Synthesis Examples 1 to 3 (sample [:I
) (II) [:IN) ) in combination with the color developer obtained in Synthesis Example 4 (sample [■]) and the microcapsules of the dye precursor solution obtained in Synthesis Example 5 (sample [■]) Examples 1-6
Coating and color development tests were conducted.

Synthesis Example 6 Using the same apparatus as in Synthesis Example 1, 491.5 y of water, sodium dodecylbenzenesulfonate s, o y e, t,
Further, 1.0 y of potassium persulfate and 0.5 f of sodium hydrogen sulfite were added as polymerization catalysts, and the temperature was raised to 70°C, followed by 9.6 y of acrylonitrile, 6527 y of methyl methacrylate, 185.6 Sl of butyl acrylate monomer, and 233 ml of 2-ethylhexyl acrylate monomer. A mixture of acrylic acid 5.52 and acrylic acid 5.21 was added at a rate of 51 per minute using a charge pump, and 1000 y of white cloudy acrylic emulsion (average particle size 0.25 μ) was obtained 7 hours after monomer charge. Ta. This had a concentration of 499%, with methyl methacrylate accounting for 18 moles of total monomers. This is referred to as a sample (VD).

Example 1 Sample (IV) on general high-quality paper (basis weight 8 Dy/rr?)
Coat a color developer with a coating roll bar of &10 so that the solid content is 5y/rri', and heat at 80°C for 1
After drying for several minutes, a developer layer was obtained.

Add the acrylic emulsion of sample [1) to this with a solid content of 2y/rr? It was coated using a coating roll bar with a temperature of 10 degrees and dried at 80° C. for 1 minute.

Next, the microcapsules of sample [■] were mixed with a solid content of 61/rr.
? It was coated using a Naruyouya 10 coating roll bar and dried at 80°C for 1 minute. As a result of the above, the developer layer,
A sample consisting of six layers including a color change time control layer and a microcapsule layer was obtained. This will be referred to as sample [A].

Example 2 According to Example 1, the color developer of sample (IV) was applied and dried in the same manner, the acrylic emulsion of sample CII) was applied and dried in the same manner, and the microcapsules of sample [v] were further applied in the same manner. , dried. This is referred to as sample CB).

Example 3 The color developer of sample (IV) was applied and dried in the same manner as in Example 1, and then the acrylic emulsion of sample (1) was applied and dried in the same manner. Engineering, dry. This will be referred to as sample [C].

Comparative Example 1 Using 50% carboxymethyl cellulose, the coating was applied and dried according to the coating method of Example 1, that is, using carboxymethyl cellulose instead of the acrylic emulsion. This will be referred to as sample [D].

Comparative Example 2 The color developer of the sample (IV) obtained in Synthesis Example 4 was applied onto general high-quality paper (basis weight 80 y/m') using a coating roll bar of Ya 10 so that the solid content was 5 y/-. Coated and heated to 80℃
After drying for 1 minute, a developer layer was obtained.

Add to this the microcapsules of sample [v] obtained in Synthesis Example 5 with a solid content of 6y/rr? It was coated using a Naruyouya 10 coating roll bar and dried at 80°C for 1 minute. In this example, a microcapsule layer was provided directly on the color developer layer, and this is referred to as sample (E).

Comparative Example-3 Instead of the acrylic emulsion of sample (1), sample (Vl
) Coating and drying were carried out in the same manner as in Example 1, except that the acrylic emulsion was used. This is referred to as sample CF).

Samples obtained in Examples 1 to 6 and Comparative Examples 1 to 6 [A
] to [F] were subjected to a discoloration test.

[Discoloration test conditions]

1. Microcapsule breaking machine Nisper Calendar (linear pressure 100 Kg/cm) 2. Microcapsule breaking temperature: room temperature 3. Temperature history 2. After breaking the microcapsules, leave at room temperature for 5 minutes, then put in the freezer at 0℃ , leave at 0°C for 2 hours, raise the temperature to 15°C, and then maintain at 15°C.

4. Two-eye color measurement (checked at any time) Next, the results of the color change test are shown in Table 1.

[Effect of the invention] As is clear from Table 1, it is clear that the discoloration time of the acrylic emulsion according to the present invention can be controlled by providing the discoloration time control layer. Example 2 (Sample [E])
After the microcapsules were destroyed, the color changed before being placed in a freezer at 0°C, and the color change density immediately increased, making it impossible to control the time at all. Further, as a result of examining carboxymethylcellulose as a time management layer, that is, in Comparative Example 1 (Sample [D]), it was eluted by moisture in the refrigerator and did not play any role in time management.

An aqueous dispersion containing the methyl methacrylate of the present invention as an essential component, that is, containing methyl methacrylate in a molar ratio of 30 or more, obtained by copolymerizing with one or more other vinyl monomers. The polymer emulsion has been found to be excellent as a composition for controlling color change time according to the present invention. On the other hand, those containing less than 30 molar percentage of methyl methacrylate rapidly changed color during heating above the set temperature, had a high discoloration density, and did not serve as the discoloration time control layer of the present invention at all.

However, when using the time management layer within the scope of the present invention, it is possible to provide a suitable induction time until the color starts to change even if the layer is exposed to a temperature higher than the set temperature, and it is clear that it is extremely effective as an indicator for temperature management. It is.

Claims (2)

[Claims] (1) Comprising microcapsules of oily substance [A]
A discoloration time control layer interposed between the layer and the layer [B] containing a substance that causes discoloration upon contact with the oily substance, and consisting of a polymer film containing 30 mol% or more of methyl methacrylate. . (2) A film of a polymer containing 30 mol% or more of methyl methacrylate was obtained by drying a polymer emulsion obtained by polymerizing a vinyl monomer containing 30 mol% or more of methyl methacrylate by an emulsion polymerization method. The color change time management layer according to claim 1, which is a continuous film.